Flat rectifier and circuit



July 4, 1939. J. SLEPIAN ET AL 2,165,075

FLAT RECTIFIER AND CIRCUIT Filed May 25, 1957 WITNESSES: INVENTORS 4 a WIf) 15 /09 Joseph S/ep/an &

' Leo/7 R Ludw/ MM BY ATTORN Y Patented July 4, 1 939 PATENT OFFICE FLATRECTIFIER AND CIRCUIT Joseph Slepian, Pittsburgh, and Leon R. Ludwig,

Forest Hills, Pa., assignors to Westinghouse Electric & ManufacturingCompany, East Pittsburgh, Pa., a corporation of Pennsylvania ApplicationMay 25, 1937, Serial No. 144,754

13 Claims. (01. PIE-354) Our invention relates to electric dischargeapparatus and has particular relation to electric discharge devices ofthe type incorporating an ignition electrode.

The discharge device to which our invention particularly relates ingeneral comprises a. cathode composedof mercury, lead, cadmium, or someother suitable metal, an anode to cooperate with the cathode and anignition electrode associated with the cathode. When a current istransmitted between the ignition electrode and the cathode, a dischargeis initiated between the anode and the cathode.

In the following discussion and in the claims, we shall refer to anelectrode of the mercury pool type. This expression shall be taken toinclude not only a cathode composed of mercury, but also cathodes ofother suitable materials which function in substantially the same manneras mercury.

The ignition electrode associated with the oathode may be disposedeither within or without the container in which the anode and cathodeare located. If it is within the container its tip may be a shortdistance from the cathode so that during the ignition period a spark isproduced between-the ignition electrode and the cathode, or it may be incontact with the cathode. In the latter case, the ignition electrode iscomposed of a highly resistant material, suchas silicon carbide, boroncarbide, silicon, boron, or a number of other suitable materials, and toinitiate a discharge, a current is transmitted through the ignitionelectrode and the electrode in contact therewith,

When we refer herein to an ignition electrode,

we mean thereby an ignition electrode of any general type includingthose located within or without the container that do not make contactwith the cathode as well as those that do make contact with the cathode.An ignition electrode of the latter type we shall specifically designateherein as an electrode of the silicon carbide device of this type, aspotis formed on the surface of the cathode, and the discharge is trtted between the spot and the anode. As th discharge passes the spotspreads and forms a number of spots all of which are located in theregion of the ignition electrode. We have found an 5 arrangement of thistype to operate satisfactorily for load requirements of moderatemagnitude for currents less than 1000 amperes, for example. However,where the current drawn by the load is very large, the region of thespots on the surface of the cathode since it is comparatively smallbecomes excessively heated, and the excessive vapor produced during thenon-arcin Period results in backflres and other di'fiiculties. Thisdimculty, while principally arising in discharge devices in which theignition electrode is of the silicon carbide type, is, of course, alsoinvolved although to a lesser extent, in discharge devices of I othertypes.

It is accordingly an object of our invention to provide a dischargedevice particularly adapted for the transmission of high currents of theorder of 1000 amperes or more, wherein the cathodeshall not becomeexcessively heated.

Another object of our invention is to provide an are discharge deviceparticularly adapted to the transformation or control of high currents.

More specifically stated, it is an object of our invention to provide adischarge device of the type having an ignition electrode that shalltransform or control heavy currents without difliculty.

In accordance with our invention, we provide a discharge device in whichthe single ignition electrode is replaced by a plurality of suchelectrodes so that for heavy currents a plurality of spot 85 regions areformedon the surface of the cathode. The ignition electrodes aresupplied in parallel from a suitable source. On the application ofpotential to the ignition electrodes simultaneously one of theelectrodes will in general effect the striking of an are before theothers. If the ignition electrodes are merely connected directly inparallel, the potential drop between the other ignition electrodes andthe catholic will be reduced u when this occurs' To make certain thatthe other ignition electrodes continue to operate, we provide couplingmeans. preferably coupling coils, between the ignition electrodes whichwhen one of the electrodes has become eflcctive, operate to impress anadditional potential on the other electrodes so that they also becomeeffective. To prevent the striking of an arc between the spot formed byone ignition electrode and the top or head of another ignition electrode(as anode), II

Y independently of each other in initiating dis-L barriers are insertedbetween the ignition elec-' trodes.

The novel features that we consider characteristic of our invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and its methodof operation,together with. additional objects and advantages thereof, will best beunderstood from the following description of specific embodiments whenread in connection with the accompanying drawing, in which:

Figure 1 is a diagrammatic view showing embodiment of our invention;

Fig. 2 is a diagrammatic view showing a modification of our invention;

Fig. 3 is a diagrammatic view showing a further modification of ourinvention; and

Pig. 4 is a view in section showing a discharge device constructed inaccordance with our invention.

The apparatus shown in Fig. 1 comprises a flat rectifier 5. Therectifier 5 consists of an evacuated container I having an insulatingcylindrical wall 9 to the upper and lower edges of which metallic discsII and i3 are sealed and thus form the bases of a hollow cylinder. Amercury pool I5 isdisposed in the bottom of the container and forms thecathode of the rectifier 5, while the upper disc'll forms the anode.

are provided into which insulating plugs l1 and I9 of circular sectioncarrying ignition electrodes 2| and 23 of the silicon carbide type aresealed. When the plugs l1 and I8 are in place, the igni-. tionelectrodes 2| and 23 dip intothe mercury l5. So that the ignitionelectrodes shall operate charges and forming pot regions on the surfaceof the mercury, any i sulating barrier 25 is provided which extends fromthe lower base I3 to a point a short distance from the anode II. Thebarrier 25 is equipped with a small opening 21 through which the mercurymay flow from one side thereof to the other.

While the fiat rectifier 5 described herein has general applicability,itis shown as utilized to supply half-wave direct current from, analternating source 29. The load 3| to be supplied other hand.:

' is adjustable.

is connected betweenone terminal of the secondary 33 of a supplytransformer 35 and the anode The other terminal of the secondary 33isconnected directly to the cathode l5 through the lower base l3. Theignition electrodes 2| and 23 are suppliedin parallel from a separatesource 31 through a suitable transformer 39, the secondary ll of whichis connected to the primary 43 of a saturable transformer 45. Thesecondary 41 of the saturable transformer 45 is connected to the mid-tap49 of a balance transformer 5| through an auxiliary rectifier 53 on theone hand and to the cathode l5 of the fiat rectifier 5 on the Theterminal taps 55 and 51 of the balance transformer 5| are connected tothe ignition electrodes 2| and 23. I

The source 31, whereby the ignition electrodes 2| and 2'3 are suppliedmay be of any general type and may have any general frequency. How- Inthe upper disc II, a pair of small openings transformer 45.

23 are positive and the cathode I5 is negative are transmitted throughthe auxiliary rectifier 53. The impulses are impressed between theignition electrodes and the cathode l5, and current flows betweentheseelectrodes and the cathode. In 5 general, an arc is ignited firstbetween the anode II and the portion of the mercury l5 associatedwlthone or the other of the ignition electrodes 2| or 23. On thestriking of this arc, an additional potential is impressed between theother 10 ignition electrode and the mercury, and the latter continues tooperate in spite of the fact that an arc has been struck first in theregion of the former electrode; Immediately after the striking of an areat the first ignition electrode 2i or 23, an 15 are is, therefore, alsostruck at the second elec- .trode. The discharge device now continues toopcrate with two spot regions and to supply rectified wave form of theimpulse may be broadened by properly selecting the dimensions of thesaturable v It is to be noted, moreover, that while our invention isshown in the Fig. 1 embodiment as applied to supply half-wave current toa load, it

may equally as well beapplied for full-wave rectification and forinversion or conversion of any general character. The number ofdischarge de vices or sets of anodes, cathodes and ignitio electrodeswill depend on the particular requirements of each case.

In the modification shown in Fig. 2, our invention is shown as, appliedto a system in which the load-is so large that two ignition electrodesdo' not provide satisfactory operation. In the modification shown inFig. 2, a discharge device 59 equipped with three ignition electrodesGI, 63 and 65 is utilized. Here again the electrodes BI,

63 and 65 are carried by insulating plugs 61; 69 and II which areinserted in the anode II in such manner that the electrodes dip in thecathode: I5. In lieu of a singlebarrier, two barriers l3 and 15 are nowprovided between the central ignition electrode 93 and the other two, GIand 65.

The three ignition electrodes 6|, 63 and are now again supplied inparallel, but the balance transformer 5| is now replaced by three pairs55 of balance coils ll, 19 and 8L One coil 83, 85 or 81 of each pair isin series with a corresponding ignition electrode SI, 83 or 65. Theremaining coils 89, 9| and 93 of the pairs are connected in series witheach other. The individual coils 83 so and 89, 85 and 9|, and 81 and 93are in inductive relation with each other, and on the striking of an arcin the region of any one of the ignition electrodes .GI, 63 or 65,current flows through the corresponding series connected coil 35 83, 85or 81 and a potential is induced in the other coil 89, 9| or 93 of thepair. The induced potential causes current to fiow through all of thecoils 89, 9| and 93 connected in series with each other and thenecessary additional potentials are induced in the coils 83, or 81connected in series with the ignition electrodes 6|, 93 or 95 in theregion of which an arc is not struck at first.

The modification shown in Fig.3 is particularly 1;

adapted for use in a system inwhich the load requirements are variableover a wide range. When light loads are supplied, it is undesirable thatmore than one ignition electrode should operate. Accordingly, we providea relay 9!, the exciting coil 91 of which is connected in the loadcircuit. When the load current is low, the relay 95 is deenergized andmaintains the supply circuit of one or the ignition electrodes, say 23,open. When the load rises above a predetermined value, the relay 85 isoperated and the supply circuit of the ignition electrode 23 is closedso that the two electrodes 2| and 23 operate in parallel as in themodification shown in Fig. l. The modification shown in Fig. 3 is asapplicable to a system incorporating a discharge device with more thantwo ignition electrodes as 59, for example, as it is to a systemincorporating a discharge device such as 5.

In Fig. 4, a discharge device 98 particularly adapted for the practiceof our invention is shown. The device comprises a container having aninsulating cylindrical wall llll which maybe composed of a ceramicmaterial or such a material as glass. The upper edge of the wall I! issecured to the flange I03 of a flanged circular metallic disc llliwhichmay function as an anode. To the lower edge a flange ill! of a flangedcupshape metallic element N19 is secured. The cupshaped element I09carries the liquid mercury l5, forming the cathode oi the dischargedevice. The ignition electrodes III and H3 are carried by lead-in wiresI I5 and I H, which in turn are sealed through the cylindrical wall IM.A barrier H9 is supported along the center of the cathode cup I09 andextends upwardly into a groove |2l cut into the anode disc Hi5. It isprovided with the customary opening I23 through which the mercury l5 mayflow from one side to the other.

It is to be noted that while the multiple spot region discharge deviceis generally highly evacuated, it may also be filled with an inert gasat a low pressure or even-at a pressure of several atmospheres.

Although we have shown and described certain specific embodiments of ourinvention, we are fully aware that many modifications are possible. Ourinvention, therefore, is not to be restricted except insofar as isnecessitated by the prior art and by the spirit of the appended claims.

We claim as our invention:

1. A discharge device comprising an electrode of the mercury pool type,another electrode to cooperate with said mercury pool electrode, andmeans for producing a plurality of emissive spot regions on the surfaceof said mercury pool electrode, said other electrode being so arrangedwith respect to said emissive regions as to cause discharges to passsimultaneously between said plurality of spot regions and said otherelectrode.

2. A discharge device comprising an electrode of the mercury pool type,another electrode to cooperate with said mercury pool electrode, and aplurality of ignition electrodes associated with spaced regions of thesurface of said mercury pool electrode, said other electrode being soarranged with respect to said spaced regions'as to cause discharges topass simultaneously between said spaced regions and said otherelectrode.

, 3. A discharge device comprising an electrode of the mercury pooltype, another electrode to cooperate with said mercury pool electrode,and a plurality of ignition electrodes of the silicon carbide type incontact with spaced regions of the surface of said mercury poolelectrode.

4. 'A discharge device comprising an electrode or the mercury pool type,another electrode to cooperate with'said mercury pool electrode, aplurality of ignition electrodes of the silicon carbide type in contactwith spaced regions of the suriace oi'said mercury pool electrode,and-barriers extending between said mercury pool electrode and saidother electrode for separating saidspaced regions. a

5. In combination, a discharge device comprising an electrode of themercury pool type, another'electrode to cooperate with said mercury poolelectrode, a plurality of ignition electrodes associated with spacedregions, of the surface of said mercury pool electrode, and couplingmeans between said ignition electrodes which, when current flows betweenone of said ignition electrodes and said mercury pool electrode,operates to increase the potential diiference between the other ignitionelectrodes and the mercury pool electrode.

6. In combination, a discharge device comprising an electrode ofthemercury pool type, another electrode to cooperate with said mercurypool electrode, a plurality of ignition electrodes of the siliconcarbide type in contact with spaced regions, of the surface 01' saidmercury pool electrode, and coupling means between said ignitionelectrodes which, when current flows between one of said ignitionelectrodes and said mercury pool i electrode, operates to increase thepotential dif ference between the other ignition electrodes and themercury pool electrode.

'7. In combination, a discharge device compristion electrodes and themercury pool electrode.

8. In combination, a discharge device comprise ing an electrode of themercury pool type, an-

other electrode to cooperate with said mercury pool electrode and meansfor producing a plurality of emissive spot regions on the surface ofsaid mercury pool electrode, and means for preventing the formation ofone of said spots so long as the discharge current between said mercurypool electrode and said other electrode is below a predetermined value.I I

9. In combination, a discharge device comprising an electrode of themercury pool type, another electrode to cooperate with said mercury poolelectrode, and a plurality of ignition elec trodes associated withspaced regions oithe surface of said mercury pool electrode, and meansfor impressing potential simultaneously on said ignition electrodes toproduce current flow between said ignition electrodes and said mercurypool electrode, said other electrode being so disposed relative to saidspaced regions that a discharge passes. to it from all said spacedregions when said current flow takes place.

10.In coinbinaiton, a discharge device comprising an electrode of themercury pool type, another electrode to cooperate with said mercury poolelectrode, and a plurality 'oi ignition electrodes associated withspaced regionslot the sur- .face of said mercury spool electrode, meansfor impressing a periodically pulsatingpotential between said otherelectrode and said mercury pool electrode, and means for impressingpotential pulses having a substantial value only for ,a time intervalthat is short compared to the trodes associated with spaced regions ofthe surface ofsaid mercury pool electrode, means for impressingpotential of peaked wave form simultaneously on said ignition electrodesto produce current flow between saidiignition electrodes and saidmercury pool electrode, and coupling means between said ignitionelectrodes,

which, when current is transmitted between one of said ignitionelectrodes and said mercury pool electrodes, operates to increase thepotential be--- tween the other ignition electrodes and said mercurypool electrode.

12. In combination, a discharge device comprising an electrode of themercury pool type,

V another electrode to cooperate-with said mercury pool electrode, and aplurality of ignition electrodes associated with spaced regions of thesurface of said mercury pool electrode, and means for impressingpotential simultaneously on said ignition electrodes to producesimultaneous current flow between said ignition electrodes and saidmercury .pool electrode, said other electrode being so disposed relativeto'said spaced regions that a discharge passes'between all said spacedregions and said other electrode when said current flow is produced.

13. In combination, a discharge device compris a ing an electrode of themercury pool type, an-

other electrode to cooperate with said mercury poolelectrode, and aplurality of ignition-elecface of said mercury pool electrode, means forimpressing a. periodically pulsating potential between said otherelectrode andsaid mercury pool,

and means for impressing potential pulses hav- .ing a substantialvalue-only during a time interval that is short compared to the periodof said pulsating potential simultaneously on said ignition electrodesto produce simultaneous current flow between said ignition electrodesand said mercury pool electrode. I

' JOSEPH SLEPIAN.

LEON R. LUDWIG.

is trodes associated with spaced regions of the sur-

